The oxygen evolution complex (OEC) of photosystem II (PSII) is intrinsically more active than any synthetic alternative for the oxygen evolution reaction (OER). A crucial question to solve for the progress of artificial photosynthesis is to understand the influential interactions during water oxidation in PSII. We study the principles of interatomic electron transfer steps in OER, with emphasis on exchange interactions, revealing the influence of delocalizing ferromagnetic spin potentials during the catalytic process. The OEC is found to be an exchange coupled mixed-valence electron-spin acceptor where its orbital physics determine the unique activity of PSII. The two unpaired electrons needed in the triplet O₂ molecule interact with the high spin state of the catalyst via exchange interactions; the optimal ferromagnetic catalyst and the resulting radical intermediates are spin paired. As a result, the active center of the CaMn₄O₅ cofactor, stimulated by the driving potential provided by photons, works as a spin valve to accelerate the formation and release of O₂ from diamagnetic H₂O.

中文翻译：

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光系统II在氧气形成和释放过程中充当自旋控制电子门

光系统II（PSII）的氧气释放复合物（OEC）本质上比氧气释放反应（OER）的任何合成替代物更具活性。解决人工光合作用进展的一个关键问题是了解PSII中水氧化过程中的影响相互作用。我们研究了OER中原子间电子转移步骤的原理，重点是交换相互作用，揭示了催化过程中离域铁磁自旋电势的影响。发现OEC是一种交换耦合的混合价电子自旋受体，其轨道物理性质决定了PSII的独特活性。三重态O _2中需要两个不成对的电子分子通过交换相互作用与催化剂的高自旋态相互作用；最佳的铁磁催化剂和生成的自由基中间体是成对的。结果，CaMn ₄ O ₅辅因子的活性中心在光子提供的驱动电势的刺激下起自旋阀的作用，以加速O ₂从反磁性H ₂ O的形成和释放。